1. Field of the Invention
The present invention relates to insulated gate transistors using semiconductors other than Si such as compound semiconductors, for example, GaAs, etc. Accordingly, a high speed and high integrated MOS IC can be fabricated.
2. Prior Art
Transistors using compound semiconductor such as GaAs are mainly Schottky type (MES) Field Effect Transistor (FET). Recently, HEMT, HBT, etc. have been developed. Silicon is applied to insulated gate FETs, particularly MOSFETs for the use in highly integrated circuits. However, usually, compound semiconductor are not applied to MOSFET. The reason is that, in large part, a good quality insulation film such as SiO.sub.2 for Si is difficult to form; in addition, there are a number of interface states in a MOS structure which use compound semiconductor. The same problems occur when Ge is used as the semiconductor.